Hello, Codeforces!

thenymphsofdelphi, lanhf, and I are delighted to invite you to take part in Codeforces Round 873 (Div. 1) and Codeforces Round 873 (Div. 2) which are going to take place at 14.05.2023 17:35 (Московское время). Participants with a rating lower than 1900 will participate in Division $$$2$$$, while participants with a rating of at least 1900 will participate in Division $$$1$$$.

In both divisions, you will be given 2 hours to solve 6 problems (one of which is divided into two subtasks), all of which were authored and prepared by me, lanhf, and thenymphsofdelphi. We would like to thank the following people who made our round possible:

• 74TrAkToR for his great coordination and help with the problems' preparation during the last 4 months.
• khuepr123 for doing nothing but being the mascot.
• A05, Kawaii, SeehEternity, yanglake, minhnhatnoe, bachbeo2007, TranGiaHuy, SanguineChameleon, HollwoQ_Pelw, socpite, uylulu, hotboy2703, generic_placeholder_name, Theoth_Normie, Kuroni, CDuongg, gamegame, AquaMoon, Huah, MagicalFlower, ugly2333, Lavine, Gary2005, Tuanlinh123, hiennoob, RDDCCD, shiv_codegen, uuzlovetree, E_huan, nixnehc, waaitg, QuangBuiCPP, errorgorn, rsj for testing our round and giving valuable feedback which helped us improve the problemset.
• MikeMirzayanov for the great Codeforces and Polygon platforms.

• Last but not least, you for participating in our round.

Scoring distribution:

Div. 1: 500 — (750+750) — 1500 — 1750 — 2500 — 3500

Div. 2: 500 — 1000 — 1250 — (1250+1250) — 2500 — 2750

We hope all of you will enjoy our problemset. Good luck and may the ratings be with you!

UPD: Congratulations to the winners!!

Also congratulations to ksun48 and Golovanov399 on (re)gaining the Legendary Grandmaster title!

UPD: Editorial

Hello Codeforces!

On May/12/2023 17:35 (Moscow time) Educational Codeforces Round 148 (Rated for Div. 2) will start.

Series of Educational Rounds continue being held as Harbour.Space University initiative! You can read the details about the cooperation between Harbour.Space University and Codeforces in the blog post.

This round will be rated for the participants with rating lower than 2100. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.

You will be given 6 or 7 problems and 2 hours to solve them.

The problems were invented and prepared by Adilbek adedalic Dalabaev, Ivan BledDest Androsov, Maksim Neon Mescheryakov and me. Also, huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all the participants!

Our friends at Harbour.Space also have a message for you:

Your Path to Success Starts at Harbour.Space Bangkok

Hello Codeforces!

We are excited to announce that we are offering 10 full scholarships to study Computer Science or Data Science at Harbour.Space, Bangkok Campus!

We invite you to apply to our university in Bangkok, Thailand, where we offer a full scholarship for qualified participants.

Our university has a vibrant and inclusive community, where you'll have the opportunity to learn from and collaborate with some of the brightest minds in your field, such as the one and only Mike MikeMirzayanov Mirzayanov. Additionally, our state-of-the-art University is designed to support your academic success and personal growth.

If you want to pursue higher education, get accreditation and expand your horizons, we encourage you to apply! As members of the Codeforces community, we recognise your talent and dedication to problem-solving, and you would make an excellent candidate for our programme.

Requirements:

Study Commitment: 3 hours/day. You will complete 15 modules (each three weeks long) in one year. The daily class workload is 3 hours, plus homework to complete in your own time.

University requirements

• CV
• High School/Bachelor's Degree
• English proficiency
• Medalist in any Programming competition is a plus!

Make sure to apply before June the 30th, 2023, to be eligible for the scholarship and reduced application fee!

We look forward to hearing from you and welcoming you to our community.

All the best, The Harbour.Space Team

UPD: Editorial is out

Hello Codeforces! （你好，代码部队）

We are glad to invite you to participate in Codeforces Round 872 (Div. 1) and Codeforces Round 872 (Div. 2) on May/08/2023 15:05 (Moscow time). Please note the unusual start time.

This round is rated for all the participants. You will be given 5 problems (one of which is divided into two subtasks) and 2 hours to solve them in each division.

Assume you are YuezhengLing, and in this round, your best friend LuoTianYi will give you several problems to solve.

(LuoTianYi is the left one and YuezhengLing is the right one)

We would like to thank:

1. RedLycoris, CrTsIr, Gyy_cj, SanweiTreap and Atomic-Jellyfish for writing the problems.

2. Artyom123 for coordinating the round.

3. MikeMirzayanov for great Codeforces and Polygon platforms.

4. He_Ren, orzdevinwang for our red suns testing the round.

5. Qingyu, zimpha, themoon, Crying, rui_er, Kevin114514, Lynkcat, lgswdn, FreshP_0325, Umi for red testing the round.

6. KbltQaQ, LHQing, Forever_Pursuit, NemanjaSo2005, geospiza, Kohaku, maoweishou, welleyth, EasonTAO, Rushroom, Gheal, rsj for orange testing the round.

7. Error_Yuan, fishy15, Lyrically. valeriu, yash_0402, smokebellew for purple testing the round.

8. LRL65, ayhan23, Zhangxuyang, Koful123, playerr17, AhmedEzzatG for blue testing the round.

9. zhy137036 for green testing the round.

10. tibinyte for gray testing the round.

11. You

    for participating in this round.

UPD: Scoring distribution:

Div.1: 500 – (500+750) – 1750 – 2250 – 3000

Div.2: 500 – 1000 – 1500 – (1000+1250) – 2750

UPD: Editorial is available here

UPD: Winners!

Div 2:

• Hex_10EFFB_
• cyfmd
• sinsop90
• Yuki__S2008
• gujialiang123

Div 1:

• jiangly
• maroonrk
• huzhaoyang
• Um_nik
• wangziji

Hey, hi Codeforces!

It's mesanu, flamestorm and me and we are very excited to invite you to Codeforces Round 871 (Div. 4)! It starts on May/06/2023 17:35 (Moscow time).

We worked swiftly to tailor the problems for this contest, so we hope you will enjoy them! We tried to make the statements short, epic and concise.

The format of the event will be identical to Div. 3 rounds:

• 5-8 tasks;
• ICPC rules with a penalty of 10 minutes for an incorrect submission;
• 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
• after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
• by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).

We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.

Only trusted participants of the fourth division will be included in the official standings table. This is a forced measure for combating unsporting behavior. To qualify as a trusted participant of the fourth division, you must:

• take part in at least five rated rounds (and solve at least one problem in each of them),
• do not have a point of 1400 or higher in the rating.

Regardless of whether you are a trusted participant of the fourth division or not, if your rating is less than 1400 (or you are a newcomer/unrated), then the round will be rated for you.

Many thanks to all testers: RedstoneGamer22, tibinyte, sandry24, jampm, haochenkang, qwexd, Vladosiya, _Vanilla_, Phantom_Performer, ScarletS, NintsiChkhaidze, keta_tsimakuridze, Dominater069, Gheal, Bakry!

And thanks to Vladosiya for russian statement translations!

We suggest reading all of the problems and hope you will find them interesting!

Good Luck and have fun!!

Are you ready for it?

UPD: Editorial is out!

Hi, Codeforces!

I am glad to invite you to take part in Codeforces Round #870 (Div. 2), which will take place on May/05/2023 17:35 (Moscow time). The round will be rated for the participants with rating lower than 2100. Participants from the first division are also welcomed to take part out of competition.

You will be given 2 hours to solve 6 problems. All the problems were authored and prepared by me. One of the problems is interactive, please read the guide of interactive problems before the contest.

I would also like to thank:

• Akulyat for excellent coordination and help improving the problems!
• arzhantsev64, InversionSpaces, Aleks5d, PO3OBAR_Bblnb, DanWallgun, Dominater069, AlperenT, Sert, sdl, Daryusz, fishy15 for testing the round and giving valuable feedback.
• Special thanks to Sert for finding a crucial bug in one of the problems!
• MikeMirzayanov for great Codeforces and Polygon platforms!

Scoring: $$$500-1000-1500-2000-2750-3250$$$.

Don't forget to read ALL the problems. I wish you good luck and high ratings!

I tried my best to create some good problems and clear short statements, so I hope you'll enjoy the round and find a problem you like :)

UPD: Editorial

UPD: Winners and First-to-solve

Div1 + Div2

Div2

First-to-solve

Hi everyone!

It's been a while since I set problems for Codeforces competitions, so I hope that you had sufficient opportunity to rest before dealing with my problems again. Oh, no-no, there's nothing to worry about! Probably! I promise!

jeroenodb and adamant (that's me!) are happy to invite you to Codeforces Round 869 (Div. 1) and Codeforces Round 869 (Div. 2) which are going to take place at 29.04.2023 17:35 (Московское время). Participants with a rating strictly lower than 1900 will participate in Division 2, while participants with a rating of at least 1900 will participate in Division 1.

All the problems are prepared by us, and we would like to thank:

• dario2994 for rejecting sufficient amount of problems for me to be able to set Oleksandr Kulkov Contest 3, for thorough and dedicated coordination and for suggesting one of the problem ideas for the round.
• izban, gamegame, tfg, fedimser, Endagorion, nor, rivalq, errorgorn, antontrygubO_o, redpanda, Runtime-Terr0r, izhang, Everule, NemanjaSo2005, ak2006, ayhan23, SlavicG, hashman, jqdai0815, willy108, madlogic, LeticiaFCS, tanus_era, nigus, Plurm, mathdude42, SajidZakaria, ace_loves_xq, InternetPerson10, alwyn, -is-this-fft-, DJeniUp and dorijanlendvaj for testing and/or valuable feedback and insights about the problems.
• MikeMirzayanov for Codeforces and Polygon and KAN for all his effort in coordinating coordinators :)

In both divisions, you will have 2 hours and 15 minutes to solve 6 problems.

Score distribution in both divisions: 500 — 1000 — 1250 — 2000 — 2500 — 3000.

Good luck and have fun!

The editorial is out.

Congratulations to the winners!

Div. 1:

1. A_G
2. tourist
3. ecnerwala
4. Rewinding
5. QAQAutoMaton

Div. 2:

1. RGB_ICPC4
2. elizazh
3. lintd
4. -LAP-
5. STOC

Hello!

On Apr/27/2023 17:35 (Moscow time) we will host Codeforces Round 868 (Div. 2).

The problems were written and prepared by Igor_Parfenov.

I would like to thank everyone who made this round possible:

• awoo, madlogic, _Israel_, Vectors_Master, BabaVoss, AlperenT, FzArK, Dominater069, m0t9_, rui_er, aryan12, purp4ever, MaherSefo, Shawerma, maomao90, satyam343, errorgorn, Glemhel for testing the round and providing feedback to the problems
• adedalic, for coordination of the round
• MikeMirzayanov, for Codeforces and Polygon platforms
• All participants

This round will be rated for participants with rating lower than 2100.

You will have 2 hours to solve 6 problems.

Score distribution: 500 — 1000 — 1250 — 2000 — 2000 — 2500.

Good luck!

UPD: Editorial

UPD: Congratulations to the Winners!

Div.2:

1. Low-Deny-Cup

2. psz6

3. BULBULBUL

4. Epyset

5. chenguoyi

Div.1 + Div.2:

1. SSRS_

2. maspy

3. Rubikun

4. heno239

5. Crystally

Hello, Codeforces!

UPD: Challenge is over. You can find results in this post

We are happy to invite you to an exciting online event: ICPC 2023 Online Spring Challenge powered by Huawei, which will start on April 13, 2023, 11:00 UTC.

In this Challenge, you will have a unique chance:

• to compete during 14 days online challenge
• to solve 1 exciting problem prepared by Huawei
• to win amazing prizes from Huawei!

As a special prize, Huawei together with ICPC Foundation will provide the travel trip to the 46th Annual ICPC World Finals in a guest role!

Everyone is welcome to participate. It is an individual competition.

ICPC 2023 Online Spring Challenge powered by Huawei (open to the public):

Start: April 13, 2023 11:00 UTC (UTC+0)
Finish: April 27, 2023 10:59 UTC (UTC+0)

We hope you'll enjoy this complex yet very exciting Challenge!

Problem

This time we’re delighted to provide you with a new challenging problem from Huawei — Buffer Sharing in Multi-Tenant Database Environment, which is prepared by Huawei 2012 Labs and Huawei Cloud Computing.

Nowadays everyone uses databases directly or indirectly. For example, databases of service providers store shopping records, transaction records, or ticket purchase records. During this challenge, you will work with the multi-tenant database, in which a single database instance is divided into multiple virtual sub-databases, serving different tenants of cloud service.

In such databases, different tenants need to be isolated from each other to prevent services from affecting each other. Therefore, buffer is considered as an important resource for management of large amount of data. When the amount of data in the database buffer reaches the maximum value, the database buffer evicts some data from the memory based on the eviction algorithm and loads new data pages from the disk. Your goal is to optimize sharing and isolation of database buffers in the multi-tenant database. While replacement algorithms considered in this contest be one of the core algorithms, we believe there are multiple approaches one can try here, and some crossover of the algorithms will also increase your chances to win!

Prizes

To be eligible for Certificates of Participation and to win prizes you are required to register at https://icpc.global/regionals/finder/Spring-Challenge-2022 by April 26th.

If you are an employee of Huawei, we invite you to participate in a competition in a special corporate scoreboard. To do this, register at the link in the secret Codeforces group. Please note that you must register even if you already have a Codeforces account, as this group has its own separate account system. Good luck!

Challenge Rules and Conditions

By participating in this Challenge, you agree to the Conditions of Participation and Challenge Rules. If you cannot access this document, please email [email protected]

Good luck, we hope this will be fun!

Update, as of April 27

Congratulations to all the participants of the ICPC 2023 Online Spring Challenge powered by Huawei!

As stated in the problem statement, the jury needs to test the latest non-zero score submissions on the final set of tests after the end of the contest. Results will be announced no later than May 1, 2023

If you registered for the Challenge by April 26th and submitted at least one response, an ICPC Certificate of Participation will be posted on your ICPC Challenge Team Record in the “Attachments” section by the end of May.

Update, as of April 29

Please ensure you register on ICPC.global using the same email as your Codeforces account no later than Fri, May 5th in order to be eligible for prizes and a Challenge certificate. If you have already registered on both platforms, please ensure your ICPC profile email matches the email used on Codeforces.

Update, as of May 1

We are glad to announce the completion of the ICPC 2023 Online Spring Challenge powered by Huawei and announce its results. Thank you very much for your interest in the competition. It was exciting for us to follow the results. We hope you enjoyed the challenges.

All tests are done, and we are glad to announce that the results in the Standings are final!

Congratulations to winners! Thanks again for your interest. We will be glad to see you in our future contests.

Hello! Codeforces Round 867 (Div. 3) will start at Apr/24/2023 17:35 (Moscow time). You will be offered 6-8 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating of 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of open hacks.

You will be given 6-8 problems and 2 hours and 15 minutes to solve them.

Note that the penalty for the wrong submission in this round is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participant of the third division, you must:

• take part in at least five rated rounds (and solve at least one problem in each of them)
• do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, and Vladosiya for coordination of our work. Problems have been created and written by: diskoteka, pavlekn, playerr17, isosto.

We would like to thank: pashka, purplesyringa, Alexdat2000, I.Gleb, Serik2003, TkachDan, maksimb2008, _--, 74TrAkToR, Gornak40, ut-k8g, Rudro25, Jostic11, yorky, tolbi, AhmetKaan, Splatjov, BF_OF_Priety, vrintle, KoT_OsKaR for testing the contest and valuable feedback.

Good luck!

UPD: Editorial